P251CPTO Enable Switch Circuit High
- Generic OBD-II code · Powertrain
- How the car detects it
- P251C is logged when the PTO enable switch line sits above its valid window, close to supply voltage. That points to a signal wire touching a battery or ignition feed, a reference that has lost its ground, or a pull-up that the switch can no longer pull down. A lost ground matters here: GM's bulletin PIP6108 for P251A on 2019–2023 medium-duty Silverado trucks sends technicians to the PTO and frame grounds first. No manufacturer documents P251C itself or gives a voltage limit. Because CARB allows monitors to pause while PTO runs and Ford's summaries clear readiness during PTO mode, a falsely high input that reads as PTO active can keep monitors from completing. Sibling codes: P251A open circuit, P251B low.
- What you may notice
- PTO engages or high idle starts without operator request
- PTO cannot be switched off normally
- Emissions readiness stays not ready
- Likely causes
- LikelySwitch signal wire shorted to a battery or ignition feed
- PossibleMissing ground on the switch or module reference
- RareSwitch stuck in the applied position
- Repair
- Medium · Often possible to do yourself.Typical cost: €0 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.